1. Field of the Invention
The present invention relates to a multi-layered golf ball having a rubber thread layer wound around the center, which attains excellent spin performance and hit feeling and provides a large carry.
2. Description of the Background Art
A multi-layered golf ball with a rubber thread layer has such a structure that rubber thread in a tensioned state is wound around a solid or liquid center to form a rubber thread layer, which is then coated with a cover. The multi-layered golf ball having such a rubber thread layer is superior in hit feeling and controllability to a two-piece golf ball with a solid core coated with a cover. However, the multi-layered golf ball has disadvantages of a high spin rate and a low angle of impact, impeding increase of carry. Thus, amateur players in general tend to prefer two-piece golf balls, which provide large carry, to the multi-layered golf ball having the rubber thread layer.
For instance, techniques of increasing the carry for a thread-wound golf ball with a solid center are described in the following conventional arts. U.S. Pat. No. 5,848,942 discloses a technique in that the center diameter is defined to be in the range of 30 to 38 mm, and the distribution of center hardness, the flexural rigidity of a cover and the like are defined to be within prescribed ranges. Moreover, U.S. Pat. No. 5,853,337 discloses that a center diameter is defined to be in the range of 30 to 38 mm and the difference between deformation under load for the center and that for a ball is defined to be in a prescribed range, while a cover with high hardness is used. Furthermore, Japanese Patent Laying-Open No. 10-201881 discloses that a center diameter is defined to be in the range of 30 to 38 mm and that deformation under load for the center, hardness of the cover and the flexural rigidity are defined to be in prescribed ranges. However, the use of these techniques cannot increase carry while maintaining the superior spin performance of the thread-wound golf ball.
The present invention is directed to solve a problem of short carry associated with a multi-layered golf ball having a rubber thread layer, and to provide a thread-wound golf ball that attains excellent spin performance and hit feeling and that produces carry equivalent to or larger than that of a two-piece solid golf ball.
According to the present invention, a thread-wound golf ball is provided, in which a center is wound by rubber thread to form a rubber thread layer, which is further coated with a cover. Here, the volume proportion of the rubber thread layer to the entire golf ball is in the range of 10 to 20%. The difference in deformation (Axe2x88x92B) is in the range of 0.5 to 0.7, where A represents deformation (mm) generated in the transition from an initial load of 98N to a final load of 1274N applied on the center, and B represents deformation (mm) generated in the transition from the initial load of 98N to the final load of 1274N applied on a thread-wound core formed by winding rubber thread around the center. The cover has Shore D hardness between 50 and 60.
Preferably, the thickness of the cover is in the range of 1.0 to 2.0 mm, and deformation (mm) A generated in the transition from the initial load of 98N to the final load of 1274N applied on the center is in the range of 3.3 to 3.9. More preferably, deformation (mm) B generated in the transition from the initial load of 98N to the final load of 1274N applied on the thread-wound core described above is in the range of 2.7 to 3.4 mm.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawing.